Polarized lightning arrestors

ABSTRACT

Systems and methods for dynamically defending a site from lightning strikes are provided. The systems and methods involve dynamically altering electrostatic fields above the site and/or dynamically intervening in lightning discharges processes in the vicinity of the site.

BACKGROUND

A lightning protection system protects a structure from damage due tolightning strikes, either by safely conducting the strike to the ground,or preventing the structure from being struck. Lightning protectionsystems are commonly installed on structures, buildings, trees,monuments, bridges and water vessels to protect from lightning orelectrical discharge damage. Lightning protection systems are also usedto protect appliances, machinery, electrical systems and electronicequipment from lightning or electrical discharge damage. Most lightningprotection systems are composed of a network of lightning rods and/orlightning arrestors (surge protectors), metallic cable conductors, andground electrodes designed to provide a low impedance path for thelightning to travel through to the ground.

A lightning rod is a metal strip or rod with a conductive cable or otherlow-resistance path to ground. A lightning rod, which is usuallyinstalled on a rooftop, provides a point well above the structure to beprotected with a very good, earthed connection. Because of its position,shape, and conductivity, the lightning rod may draw energy (current)from a lightning discharge and diverts the energy to ground via theconductive cable to ground, thus preventing damage to the structure.FIG. 1, which is adapted from Tesla U.S. Pat. No. 1,266,175, shows anearly lightning rod.

A lightning arrestor is a device, which is typically used for protectingelectronic or electrical equipment from lightning by diverting anysurges of high-voltage electricity caused by atmospheric discharges toground. The lightning arrestor includes an “active” element, whichswitches from a non-conductive state to a conductive state in responseto a surge in voltage. The active element in its conductive stateprovides a short i.e. a path for the high voltage to go to ground,bypassing the electronic or electrical equipment to be protected. Inother words, the active element acts as an over-voltage release valve.The active element of a lightning arrestor may, for example, be a metaloxide varistor, a transient suppression diode, a gas discharge tube, aspark gap, a crowbar (circuit) using a Zener diode driving the gate of asilicon-controlled rectifier (SCR) latch, or any other suitable device.For convenience in description, both lightning rods and lightningarrestors may be referred to as lightning arrestors herein.

Consideration is now being given to improving traditional lightningprotection systems.

SUMMARY

Approaches to defend a site from lightning strikes are provided.Illustrative approaches involve altering electrostatic fields above thesite and/or dynamically intervening in lightning discharge processes inthe vicinity of the site.

In an exemplary approach, a system for defending a site includes aplurality of lightning arrestors. The electrostatic fields above thesite are modified by the system to influence overhead electricaldischarge processes. One or more voltage biasing elements are arrangedto bias a first of the lightning arrestors to a different respectivepotential than a second of the lightning arrestors. The respectivepotentials to which the lightning arrestors are biased are below acorona discharge limit.

In another exemplary approach, a system for defending a site involvesaltering the path of an overhead lightning discharge. The illustrativesystem includes a sensor network arranged to detect a lightning stepleader descending from an overhead atmospheric charge accumulationand/or an upward rising earth streamer. The system includes devices(e.g., lasers, charge guns, etc.) for making ionized path segments inthe atmosphere to extend or limit progress of the lightning step leaderand/or earth streamer in selected directions.

BRIEF DESCRIPTION OF THE FIGURES

In the accompanying drawings:

FIG. 1 is an illustration of a lightning rod and a groundingarrangement.

FIG. 2 is a block diagram illustrating components of an exemplarylightning protection system, in accordance with the principles of thesolutions described herein;

FIG. 3 is a schematic illustration of an exemplary lightning arrestor inbiased and unbiased states, in accordance with the principles of thesolutions described herein;

FIG. 4 is schematic illustration of an exemplary sequence of lightningarrestors in varying biased states, in accordance with the principles ofthe solutions described herein;

FIG. 5 is an illustration of a lightning discharge or flash process asmay be recorded with a streak-camera photograph.

FIG. 6 is a block diagram illustrating components of another exemplarylightning protection system, in accordance with the principles of thesolutions described herein;

FIG. 7 is a schematic illustration of an exemplary deployment oflightning protection system of FIG. 6 deployed to protect a site fromlightning strikes, in accordance with the principles of the solutionsdescribed herein;

FIG. 8 is a flow diagram illustrating an exemplary method for lightningprotection, in accordance with the principles of the solutions describedherein;

FIG. 9 is a flow diagram illustrating another exemplary method forlightning protection, in accordance with the principles of the solutionsdescribed herein;

FIG. 10 is a block diagram illustrating components of yet anotherexemplary lightning protection system, in accordance with the principlesof the solutions described herein;

FIG. 11 is a flow diagram illustrating yet another exemplary method forlightning protection, in accordance with the principles of the solutionsdescribed herein;

FIG. 12 is a block diagram illustrating components of still anotherexemplary lightning protection system, in accordance with the principlesof the solutions described herein; and

FIG. 13 is a flow diagram illustrating still another exemplary methodfor lightning protection, in accordance with the principles of thesolutions described herein.

Throughout the figures, unless otherwise stated, the same referencenumerals and characters are used to denote like features, elements,components, or portions of the illustrated embodiments.

DESCRIPTION

In the following description of exemplary embodiments, reference is madeto the accompanying drawings, which form a part hereof. It will beunderstood that embodiments described herein are examples, but are notmeant to be limiting. Further, it will be appreciated that the solutionsdescribed herein can be practiced or implemented by other than thedescribed embodiments. Modified embodiments or alternate embodiments maybe utilized, in the sprit and scope of the solutions described herein.

In an exemplary approach for protecting a site from lightning strikesemanating from overhead charge accumulations, electrostatic fields abovethe site may be modified by applying external voltages to airtermination networks deployed at the site. The modification of theelectrostatic fields, which may be dynamic in response to changingweather conditions, may be expected to help dissipate the overheadcharge accumulations and/or relocate possible lightning strikes awayfrom the protected site.

FIG. 2 shows exemplary components of a lightning protection system 200in accordance with the principles of the solutions described herein.Lightning protection system 200 includes an air termination network 210,voltage biasing elements 212, a down conductor system 220, and an earthtermination network 230. System 200 may further include an optionalsensor network 240 configured to monitor and report, for example,weather, atmospheric, or other environmental conditions that may bepresent or anticipated at or about lightning protection system 200 andprotected structures. Sensor network 240 may generate appropriatereporting signals for use by lightning protection system 200 and/orother external devices. System 200 also may include an optionalcontroller 250. Operation of various components of lightning protectionsystem 200 may be supervised by controller 250 or other controllersystems that may be located nearby or distant from lightning protectionsystem 200 and protected structures. In one approach, for example, theoperation of voltage biasing elements 212 and/or sensor network 240 maybe controlled through a remote control system located at a differentfacility or site, for example, through wireless, wired, IP protocol orother approaches.

Air termination network 210 may include one or more lightning arrestorsarranged to interact with or intercept an atmospheric electricaldischarge or lightning stroke. The number and type of lightningarrestors in air termination network 210 may be selected inconsideration of the type of structure or site to be protected by airtermination network 210. When the structure to be protected is abuilding, air termination network 210 may, for example, include aplurality of vertical metal (e.g., copper or aluminum) lightning rodsdisposed on the roof of the building. When the structure to be protectedis a high voltage power transmission line, air termination network 210may, for example, include conducting ropes, cables, netting, mesh,extended surfaces and/or rods. It will be understood that structures andsites that can be protected by air termination network 210 are notlimited to a particular type or size of structures (e.g., a building)but may include combinations of several types of structures (e.g.,buildings, power lines, transmission line towers, antennas, etc.) of anysize or extent.

In system 200, down conductor system 220 connects air terminationnetwork to an earth termination network 230. Down conductor system 220may be suitably arranged to provide a lightning stroke current a lowimpedance path to earth termination network 230. Down conductor system220 may include any suitable arrangement of conducting cables and/orwires for this purpose. Likewise, earth termination network 230 mayinclude any combination of earthed rods, plates and/or conductorsarranged for safe dissipation of the stroke current into the ground or aground equivalent.

Further, in system 200, voltage biasing elements 212 may be EMF sources,which are coupled to one or more individual lightning arrestors in airtermination network 210. Voltage biasing elements 212 may, for example,include capacitors, a voltage amplifier and/or very high impedancehigh-voltage (˜0.1-1 MV; ˜10-1000 micro amp) power supplies. The powersupplies may, for example, be energized by solar photovoltaic arraysdeployed in outdoor locations.

Voltage biasing elements 212 may be disposed anywhere between ground andlighting arrestors' tips. Thus, voltage biasing elements 212 may bedisposed in air termination network 210 and/or down conductor system 220as convenient or appropriate. It will be understood that voltage biasingelements 212 may be provided with protective active elements (not shown)configured to block or divert over-voltages and/or over-currents, whichmay arise in the operation of air termination network 210. Voltagebiasing elements 212 may be configured to raise or lower the potentialat about an end of a lighting arrestor by an applied potential amountV_(b) relative to a reference potential. The reference potential may,for example, be another lighting arrestor's potential, ground potential,or other intermediate potential. Further, voltage biasing elements 212may be configured to apply the potential V_(b) continuously orintermittently over selected time intervals.

Raising or lowering a lighting arrestor's potential by a bias voltageV_(b) may provide polarizing fields above the lighting arrestor thatinteract with overhead atmospheric charge accumulations. The polarizingfields may allow system 200 to preferentially source or sink electriccharge to or from overhead atmospheric charge accumulations via thebiased, relative to an identical unbiased or ‘simply grounded’ lightningarrestor in the same location at the same instant-in-time. From anotherperspective view, biasing the lightning arrestor may provide a ‘virtual’lightning arrestor of much greater “effective height” than anything elsein the vicinity. The effective height of the lightning arrestor may beselected by applying a suitable amount of bias voltage so that allproximate objects are robustly defended from the damaging effects oflightning stroke currents.

FIG. 3 shows an example of a lightning arrestor rod A with a voltagebiasing element 310 disposed toward its base. No bias voltage is appliedto lightning arrestor rod A in the condition shown, for example, to theright in FIG. 3. Application of a bias voltage V_(b) to lightning rod Aas shown, for example, to the left in FIG. 3, displaces or polarizeselectrical fields near the top end of the rod and increases theeffective length of the rod. The amount and sign of bias voltage V_(b)applied may be limited so that rod A operates below a corona dischargelimit. However, the amount and sign of bias voltage V_(b) may besufficient so that the displaced or polarized electrical fields aboutvoltage-biased rod A′ can interact with and modify overhead atmosphericcharge accumulations in a different manner than the unbiased rod A.

Modification of overhead atmospheric charge accumulations by polarizingfields created by the bias voltage applied to the lightning arrestor maybe expected to provide spatial and temporal control over dissipation oflightning stroke energy emanating from the overhead chargeaccumulations. The amount of bias voltage may, for example, be selectedto break down air and provisionally or peremptorily prepare asufficiently large conducting path between ground and the overheadcharge accumulations to reduce the latter. The time interval over whichthe bias voltage is applied may be selected in consideration of thedynamics of overhead charge accumulations and the rates of chargedissipation by the “virtual” portion of the lightning arrestor createdby the bias voltage. Such consideration may include consideration of therates of charge dissipation by the bias voltage-induced virtual portionof the lightning arrestor relative to, for example, a meteorologicallymaximum feasible rate of accumulation of overhead charges. It may benecessary to apply the bias voltage to the lightning arrestor onlymomentarily or only as a transient to prepare a conducting path fordissipating dangerous overhead charge accumulations.

The amount and application times of bias voltage applied to rod A may beselected to provide adequate provisional or preemptory conductive pathsfrom overhead charge accumulations to ground, which make it effectivelyimpossible for a lightning bolt to strike within a select distance inspace and time from lightning rod A. Suitable theoretical or empiricalmodels of atmospheric charge accumulations and their interactions withlightning arrestors may be developed and used to compute the amount andtiming of bias voltages applications required to prevent a lightningbolt from striking within a selected distance from lightning rod A.

With renewed reference to FIG. 2, controller 250 may have any suitablemechanical or electromechanical structure. Further, controller 250 mayoptionally include or be coupled to a processor 252 and/or aprogrammable interface 254. Controller 250 may be configured toimplement suitable biasing schedules (e.g., timing, amount and sign ofbias voltages Vb applied by voltage biasing elements 212) for variouslightning arrestors. Controller 250/processor 252 may determine thesuitable biasing schedules based, for example, on signals generated bysensor network 240 and/or other external devices. Algorithms fordetermining the suitable biasing schedules and the responses of system200/controller 250 to various sensor network 240 signals and/or othercontrol signals may be set up or programmed by a user, for example,through programmable interface 254.

Processor 252 may use the algorithms to compute model lightningstrike-safe distances and corresponding voltage biasing schedules forthe lightning arrestors in air termination network 210. Processor 252may be configured to obtain air termination network 210 conditions andweather conditions at or about air termination network 210 and itsprotected structures from sensor network 240 or other external sources(e.g., meteorological stations). Processor 252 may be further configuredto develop prophylactic voltage biasing schedules to prevent imminentlightning strikes from present and/or forecasted overhead chargeaccumulations. Further, controller 250 may be configured to dynamicallyimplement the prophylactic voltage biasing schedules generated by theprocessor or other voltage biasing schedules on the lightning arrestorsin air termination network 210.

The development of the voltage biasing schedules may also includeconsideration of the spatial distribution of lightning arrestors in airtermination network 210, and consideration of a user-definedprioritization or ranking of different portions of the protectedstructure or site according to importance for protection fromatmospheric electrical discharges. A user-defined ranking may, forexample, deem a portion of a protected structure that houses computer orother sensitive electronic equipment as needing more or betterprotection from lightning strikes than other portions of the protectedstructure that do not house such equipment. Accordingly, the voltagebiasing schedules may include spatial variation in the biasing of adistribution of lightning arrestors in air termination network 210 toprovide more or better lightning strike protection for the priorityportions of the protected structure.

More generally, variation in potential biasing of a spatial distributionof lightning arrestors may be used to control a location of theprovisional or preemptive conducting path from overhead chargeaccumulations to ground. FIG. 4 shows, for example, an air terminationnetwork 400 deployed to defend site 410. Different lightning arrestors(e.g., rods 402-408) in air termination network 400 may be charged byrespective voltage biasing elements to different respective potentialsto defend site 410 from atmospheric electrical discharges. At least onelighting arrestor may be charged to a potential in anticipation of alightning strike. A first lightning arrestor (e.g., rod 402) may becharged to a positive potential and a second lightning arrestor (e.g.,rod 404) may be charged to a negative potential relative to a site orreference potential. Further, air termination network 400 may include asequence of alternating positively and negatively charged lightningarrestors (e.g., rods 406 and 408).

Site 410 defended by deploying air termination network 400 may, forexample, be an overhead AC transmission line from lightning oratmospheric electrical discharges. In this example, air terminationnetwork 400 may include a sequence of lightning arrestors that arealternating positively and negatively charged to potentials havingmagnitudes greater than a peak line voltage on the overhead ACtransmission line. Alternatively or additionally, site 410 by deployingair termination network 400 may include an overhead DC transmissionline. In this example, air termination network 400 may include asequence of lightning arrestors that are respectively charged topotentials alternately greater and less than a line voltage on theoverhead DC transmission line.

It will be understood that the lightning arrestors in air terminationnetwork 400 are shown to have rod-like long shapes (e.g., rods 402-408)only for example. In practice the lightning arrestors may have anygeometrical shape appropriate for defending a particular site fromlightning strikes. A lightning arrestor may have a long shape (e.g.,rods, wires, Franklin-type lightning rods, spikes, etc.) that isconducive to directional emission of charges from an arrestor end.Alternatively or additionally, a lightning arrestor may have a roundedor planar shape having an extended surface (e.g., panels, plates,conducting shields, walls of Faraday cage-like structures, etc.) thatmay emit charges non-directionally or less directionally than along-shape lightning arrestor. At least one of the plurality oflightning arrestors in an air termination network may have a rod-,rope-, cable-, wire-, mesh-, netting-, strip-, plate-, panel-, wall-,and/or other extended surface-shape.

In another exemplary approach for protecting a site from lightningstrikes from overhead charge accumulations involves a dynamic defense.In this approach, artificial man-made conducting channels of ionized airmay be created in the atmosphere in a controlled manner. The artificialman-made conducting channels of ionized air may be expected to helpdissipate overhead charge accumulations and to reduce damage fromrandomly located lightning strikes.

A lightning discharge or flash (e.g., a cloud-to-ground discharge) is atransient current of high intensity often spanning several kilometers. Acloud-to-ground discharge may be made up of a series of partialdischarges separated in time by 40-50 milliseconds and lasting about 200milliseconds for a total flash.

FIG. 5, which is adapted from Niels Jonassen, Environmental ESD, PartII: Thunderstorms and Lightning Discharges, Compliance Magazine, (2005),shows characteristic features of a cloud-to-ground lightning dischargeor flash as they would appear on a streak-camera photograph. Eachlightning discharge starts with a predischarge or leader (“steppedleader” or “step leader”) that propagates from the cloud to the groundin weakly luminous steps. The stepped leader, which is a channel of highionization and charge, appears to move downward from the cloud inluminous steps about 50 m in length. The time between steps is about 50microseconds, during which time the intensity of the stepped leader istoo weak to be observed. As the step leader approaches the earth,objects on the earth surface begin responding by growing positivestreamers. When the downward stepped leader brings negative charge athigh potential close to the ground, the field strength at ground levelmay be high enough to cause ionization and make a discharge (earthstreamer) move from the ground to the leader. When the two dischargesmeet, the step leader is effectively grounded and its conductive channelmay support a very luminous main or return stroke. The main or returnstroke may carry strong currents (e.g., 10-20 kA during the first fewmicroseconds). Considerable amounts of energy, which are commonlyassociated with a lightning strike, are dissipated by the main or returnstroke in the ionized channel established by the stepped leader. Afterthe current has ceased to flow down the stepped leader channel, theremay be a pause of about 20 to 50 milliseconds. After which, ifadditional charge is available in the cloud at the top, another leader(“dart leader”), which is not stepped, may propagate down the alreadyestablished but decaying ionized channel. The dart leader carries thecloud potential to the vicinity of the ground. Again, a main or returnstroke can be produced. All strokes that use the same ionized channel toground constitute a single cloud-to-ground lightning flash. Thecombination of the leader and the return stroke is known as a stroke. Alightning flash might be made up of one to a few tens of strokes.

FIG. 6 shows exemplary components a lightning protection system 600 fordynamic defense of a site from lightning strikes. System 600 involvespreparing or creating charge conducting channels or paths in theatmosphere in a controlled manner to dissipate atmospheric chargeaccumulations (e.g., in clouds). A charge conducting channel or path mayinclude regions of the atmosphere having modified dielectric properties,excited molecules and/or ionized molecules, which make it likely tosupport flow of currents therethrough.

System 600 includes a sensor network 610 arranged to detect lightningstep leaders and/or return strokes in the vicinity of a defended site,and a device 620 for preparing or creating charge conducting channels inthe atmosphere. System 600 may also include other lightning protectioncomponents (e.g., air termination network 210) for protecting the site.Further, system 600 includes a controller/processor 630, which isconfigured to supervise or co-ordinate operation of system components.Controller/processor 630 may have any suitable mechanical orelectromechanical structure, and include an optional programmableinterface. In one approach, controller/processor 630 and other systemcomponents may be linked, for example, through wireless, wired, IPprotocol or other approaches.

Device 620 for preparing or creating charge conducting paths or channelsin the atmosphere may be any suitable device that can ionize air atselected locations or paths in the atmosphere by, for example, directingionizing energy or supplying charges at the selected locations. Device620 may, for example, be an energy or particle beam generator. In anexemplary implementation of system 600, device 620 may, for example,include a high energy pulsed laser and/or a high energy capacitordischarge circuit and a ground charge injector.

Sensor network 610 may include one or more electrical, magnetic, opticaland/or other sensors configured to determine the location and timing ofstepped leaders that may precede main or return lightning strokes at orin the vicinity of the defended site. Sensor network 610 may alsoinclude sensors configured to measure earth potentials and/or determinethe location and timing of earth streamers that may develop into areturn lightning stroke in the vicinity of the defended site. Sensornetwork 610 may be configured to generate appropriate reporting signalsfor use by lightning protection system 600 and/or other external devicesfor dynamically defending the site from lightning strikes.

FIG. 7 shows an exemplary deployment of system 600 to defend a site 710from lightning strikes. In this exemplary deployment, device 620 mayinclude a laser 622, and a charged capacitor discharging circuit 624coupled to a ground charge injector 626. System 600/controller 630 mayinclude suitable algorithms or routines for responding to step leaderactivity, ground streamer activity, and/or ground potential valuesdetected in the vicinity of the defended site 710 by sensor network 610.The algorithms or routines may include an assessment of a likelylocation of an impending lightning strike based, for example, on thelocations and timing of the detected step leaders, earth streamers,and/or measured earth potential values. In response to the assessment,system 600/controller 630 may operate or activate device 620 to preparecharge conducting channels or paths (e.g., paths segments 712 and 714)in the atmosphere to modify the course of the impending lightningstrike.

In an exemplary mode of operation of system 600, laser 622 may, forexample, direct an ionizing energy beam to create an ionized pathsegment (712) extending or limiting a detected stepped leader in aparticular direction. Alternatively or additionally, laser 622 maydirect an ionizing energy beam to create an ionized path segment (714)extending or limiting an earth streamer in a particular direction. Theionized path segments 712 and/or 714, which are artificially created bydevice 620, may be suitably oriented to direct the stepped leader awayfrom defended site 710 or to connect the stepped leader to an earthstreamer at a selected ground location (e.g., location A) at a safedistance from defended site 710. In this manner, system 600 may preparean attractive conduction path (B) directed away from defended site 710for the impending lightning strike.

In an additional or alternate mode of operation, system 600 may helpgenerate attractive conduction path (e.g., path D) directed away fromdefended site 710 for the impending lightning strike by modifying groundpotentials at select locations. In this mode of operation, chargedcapacitor discharging circuit 624 may provide charge, which is theninjected into the earth at a selected earth location (e.g., location C)by ground charge injector 626. The amount of the injected charge may beselected to be sufficient to raise the local earth potential toencourage an earth streamer at location C to grow toward and connect toan overhead stepped leader. In this manner, system 600 may prepare anattractive conduction path (D) directed away from defended site 710 forthe impending lightning strike.

Methods for protecting sites from atmospheric electrical dischargesinclude dynamically altering electrostatic fields above the site and/ordynamically intervening in lightning discharges processes in thevicinity of the site. FIGS. 8 and 9 show exemplary methods 800 and 900for defending a site from lightning.

Method 800, which involves dynamically altering electrostatic fieldsabove the site, includes disposing a plurality of lightning arrestors ata site (810), and biasing various lightning arrestors differently toalter or modify the electrostatic potential distributions above the site(820). The biasing of the various lightning arrestors may have a spatialvariation based, for example, on consideration of relative importancesof protecting different portions of the site from lightning. At leastone of the lightning arrestors may be biased to a different respectivepotential than a second of the lightning arrestors. Method 800 mayinclude sensing overhead electrical activity and/or weather conditionsto guide a biasing schedule of the various lightning arrestors.

Method 900, which involves dynamically intervening in lightningdischarge processes in the vicinity of the site, includes sensing alightning step leader leaving an overhead atmospheric chargeaccumulation (910) and/or an upward earth streamer, and in response to adetected step leader, preparing a charge conductive path through theatmosphere to ground to divert the lightning strike or otherwisedissipate the overhead atmospheric charge accumulation (920). In method900, preparing a charge conductive path through the atmosphere to groundmay include firing a laser beam through the atmosphere to ionize air,injecting charges in the atmosphere, and/or a ground location toencourage the overhead charge accumulation to dissipate, for example,along a particular path away from the site.

The detailed description herein has set forth various embodiments of thedevices and/or processes via the use of block diagrams, flowcharts,and/or examples. Insofar as such block diagrams, flowcharts, and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts, or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or virtually any combination thereof. In one embodiment,several portions of the subject matter described herein may beimplemented via Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs), digital signal processors (DSPs), orother integrated formats. However, those skilled in the art willrecognize that some aspects of the embodiments disclosed herein, inwhole or in part, can be equivalently implemented in integratedcircuits, as one or more computer programs running on one or morecomputers (e.g., as one or more programs running on one or more computersystems), as one or more programs running on one or more processors(e.g., as one or more programs running on one or more microprocessors),as firmware, or as virtually any combination thereof, and that designingthe circuitry and/or writing the code for the software and or firmwarewould be well within the skill of one of skilled in the art in light ofthis disclosure. In addition, those skilled in the art will appreciatethat the mechanisms of the subject matter described herein are capableof being distributed as a program product in a variety of forms, andthat an illustrative embodiment of the subject matter described hereinapplies regardless of the particular type of signal bearing medium usedto actually carry out the distribution. Examples of a signal bearingmedium include, but are not limited to, the following: a recordable typemedium such as a floppy disk, a hard disk drive, a Compact Disc (CD), aDigital Video Disk (DVD), a digital tape, a computer memory, etc.; and atransmission type medium such as a digital and/or an analogcommunication medium (e.g., a fiber optic cable, a waveguide, a wiredcommunications link, a wireless communication link (e.g., transmitter,receiver, transmission logic, reception logic, etc.), etc.).

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.For example, FIG. 10 shows another exemplary lightning protection system1000. System 1000 may include a sensor or sensor arrangement 1010arranged to detect a lightning step leader descending from and/or anupward earth streamer ascending toward an atmospheric chargeaccumulation. Sensor or sensor arrangement 1010 may, for example, besimilar to or the same as sensor arrangement 610 (FIG. 6). System 1000further includes a device 1020 coupled to the sensor or sensorarrangement 1010. Device 1020 may be a charge-emitting device configuredto inject charges in the ground (e.g., a capacitor, a current source,devices 624 and 626, etc.). Device 1020 may be configured to alter aground potential in response to the detected step leader and/or upwardearth streamer. When system 1000 is deployed at a site, device 1020 maybe arranged to alter the ground potential to direct a lightning strikeaway from the site. Device 1020 may be arranged to inject charges at orabout a selected ground termination location for a lighting strike.

FIG. 11 shows another exemplary lightning protection method 1100, whichmay for example, utilize system 1000, for protecting a site. Method 1100includes sensing a lightning step leader descending from and/or anupward earth streamer ascending toward an atmospheric chargeaccumulation (1110), and altering a ground potential in response to thedetected step leader and/or upward earth streamer (1120). Altering theground potential may include injecting charges in the ground to, forexample, direct a lightning strike away from a site. The charges may beinjected at or about a selected ground termination location for alighting strike.

Further, for example, FIG. 12 shows yet another exemplary lightningprotection system 1200 for actively protecting a site. Active lightningprotection system 1200 may include a sensor arrangement (1210) arrangedto detect one or more of a lightning step leader descending from anatmospheric charge accumulation and/or an upward earth streamerascending toward the atmospheric charge accumulation. Sensor arrangement1210 may be configured to detect or sense, for example, a strength, alocation, a direction and/or a timing of the lightning step leader, theupward earth streamer, and/or the atmospheric charge accumulation.Further, sensor arrangement 1210 may include a sensor arranged to detector sense a weather condition, a site potential value, and/or ageopotential value.

System 1200 may further include a risk-assessment processor or circuitry(1220), which is coupled to sensor arrangement 1210 and configured toprovide a risk assessment of a lightning strike, and an arrangement ofone or more reconfigurable lightning protection elements (1230)responsive to the risk assessment of a lightning strike. System 1200 mayalso include suitable control circuitry 1240 configured to reconfigurethe one or more reconfigurable lightning protection elements in responseto the risk assessment of a lightning strike.

The arrangement of one or more reconfigurable lightning protectionelements 1230 may, for example, include one or more adjustable-heightlightning arrestors whose heights are adjustable in response to the riskassessment of a lightning strike. Alternatively or additionally,arrangement 1230 may include one or more lightning arrestors whosepotentials are adjustable in response to the risk assessment of alightning strike (e.g., lightning arrestors 404-408, air terminationnetwork 400 (FIG. 4)). Alternatively or additionally, arrangement 1230may include a device arranged to prepare a charge conductive paththrough the atmosphere in response to the detected step leader and/orthe detected upward earth streamer. The device may, for example, be thesame or similar to the devices in systems 600 and 1000 (e.g., device620, laser 622, capacitor discharge circuit 624, ground injector 626,device 1020, etc.).

System 1200/control circuitry 1240 may be configured so that aready-to-operate status of system components (e.g., arrangement of oneor more lightning protection elements 1230, device 620, laser 622,capacitor discharge circuit 624, ground injector 626, device 1020, etc.)is configured to be responsive to progressive or developing riskassessments of a lightning strike.

The charge conductive path through the atmosphere prepared by system1200 in response to the detected step leader and/or the detected upwardearth streamer may include excited molecules and/or ionized molecules. Aposition and/or direction of the charge conductive path may be selectedor determined in response to a location and/or direction of the detectedstep leader, the detected upward earth streamer and/or atmosphericcharge accumulation. The charge conductive path may have characteristicsor properties that are, for example, similar to the charge conductivepaths prepared by system 600 described herein with reference to FIGS.5-7.

FIG. 13 shows another exemplary lightning protection method 1300, whichmay for example, utilize system 1200, for actively protecting a site.Method 1300 may, for example, include sensing one or more of a lightningstep leader descending from and/or an upward earth streamer ascendingtoward the atmospheric charge accumulation (1310) at or about the site,making or providing a risk assessment of a lightning strike at or aboutthe site based on results of the sensing (1320), and reconfiguring anarrangement of one or more lightning protection elements disposed at orabout a site in response to the risk assessment of a lightning strike(1330).

When the arrangement of one or more lightning protection elementsincludes adjustable-height lightning arrestors, reconfiguring thearrangement of lightning protection elements 1330 may include adjustingthe heights of the lightning arrestors in response to the riskassessment of a lightning strike.

In general, detailed, additional and alternate processes and actions inmethod 1300 may be a function of the nature and type of the arrangementof one or more lightning protection elements disposed at or about asite. Method 1300 may, for example, include one or more steps, actionsand processes described herein (e.g., with reference to methods 800,900, and 1100) as appropriate to the nature and type of the arrangementof one or more lightning protection elements disposed at or about asite. For example, when the lightning protection elements are the sameor similar to lightning arrestors 402-408 of air termination network 400(FIG. 4), method 1300 may include processes and actions that are thesame or similar to those described with reference to method 800. Whenthe lightning protection elements include devices to prepare conductingpaths through the atmosphere, for example, in response to lightning stepleaders or upward earth streamers (FIGS. 6, 7, and 10), method 1300 mayinclude processes and actions that are the same or similar to thosedescribed with reference to methods 900 and 1100.

The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

The invention claimed is:
 1. A system, comprising: a plurality oflightning arrestors comprising conductors located and extending aboveground level and electrically terminating at ground; and one or morevoltage biasing elements coupled to the plurality of lightning arrestorsand arranged to bias a first of the lightning arrestors to a differentrespective potential than a second of the lightning arrestors; one ormore sensors configured to monitor atmospheric conditions; and acontroller, receiving information representative of the atmosphericconditions, the controller arranged to selectively adjust the one ormore voltage biasing elements based on the information, wherein theplurality of lightning arrestors comprises a sequence of lightningarrestors that are biased to potentials, which are alternately greaterand less than a line voltage on an overhead DC transmission line.
 2. Thesystem of claim 1, wherein the one or more voltage biasing elements arearranged to bias the first of the lightning arrestors to a non-zeropotential relative to a local ground potential.
 3. The system of claim1, wherein the one or more voltage biasing elements are arranged to biasthe plurality of lightning arrestors to establish a potential gradientacross the plurality of lightning arrestors.
 4. The system of claim 1,wherein the one or more voltage biasing elements are arranged to biasthe first of the lightning arrestors to a potential that is below acorona discharge limit.
 5. The system of claim 1, wherein the one ormore voltage biasing elements comprise an EMF source.
 6. The system ofclaim 1, wherein the one or more voltage biasing elements comprise acapacitor and/or a voltage amplifier.
 7. The system of claim 1, whereinthe one or more voltage biasing elements comprise a photovoltaic array.8. The system of claim 1, wherein at least one of the plurality oflightning arrestors has a rod-, a rope-, a cable-, a wire-, a netting-,a strip-, a plate-, a panel-, a wall-, and/or an extended surface-shape.9. The system of claim 1, wherein at least one of the plurality oflightning arrestors is arranged to emit charges substantiallynon-directionally.
 10. The system of claim 1, wherein at least one ofthe plurality of lightning arrestors is arranged to emit chargessubstantially directionally.
 11. The system of claim 1, wherein thefirst of the lightning arrestors and the second of the lightningarrestors are spaced less than a critical distance apart so that zonesof protection of the first and second lightning arrestors overlap. 12.The system of claim 1, wherein the first of the lightning arrestors isbiased to a positive potential, and the second of the lightningarrestors is biased to a negative potential.
 13. The system of claim 1,disposed at a site, wherein the first of the lightning arrestors isbiased to a positive potential relative to a site potential, and thesecond of the lightning arrestors is biased to a negative potentialrelative to the site potential.
 14. The system of claim 13, wherein theplurality of lightning arrestors comprises a sequence of lightningarrestors that are biased to positive and negative potentials, whichhave magnitudes greater than a peak line voltage on the overhead ACtransmission line.
 15. The system of claim 1, wherein the plurality oflightning arrestors comprises a sequence of positively and negativelybiased lightning arrestors.
 16. The system of claim 1, wherein theplurality of lightning arrestors comprises a sequence of lightningarrestors that are positively and negatively biased with respect to asite potential.
 17. The system of claim 1, which is deployable toprotect an overhead AC transmission line from an atmospheric electricaldischarge.
 18. The system of claim 1, which is deployable to protect anoverhead DC transmission line from an atmospheric electrical discharge.19. The system of claim 1, further comprising, at least one sensorarranged to sense a weather condition.
 20. The system of claim 1,wherein the controller is arranged to bias the first of the lightningarrestors in response to a weather condition and/or an anticipatedweather condition.
 21. The system of claim 1, wherein the controller isarranged to bias the first of the lightning arrestors in response to ageopotential value.
 22. The system of claim 1, wherein the controller isarranged to bias the first of the lightning arrestors to prepare aconducting path from an overhead charge accumulation to ground.
 23. Amethod, comprising: providing, at a site, a plurality of lightningarrestors comprising conductors located and extending above ground levelat the site and electrically terminating at ground; monitoringatmospheric conditions by one or more sensors; receiving informationrepresentative of the atmospheric conditions, by a controller, thecontroller arranged to selectively adjust one or more voltage biasingelements based on the information; and biasing a first of the lightningarrestors to a different respective potential than a second of thelightning arrestors based on the information, wherein biasing a first ofthe lightning arrestors to a different respective potential comprisesbiasing a sequence of lightning arrestors to potentials that arealternately greater and less than a line voltage in an overhead DCtransmission line.
 24. The method of claim 23, wherein biasing a firstof the lightning arrestors comprises biasing the first of the lightningarrestors to a non-zero potential relative to a local ground potential.25. The method of claim 23, wherein biasing a first of the lightningarrestors comprises biasing the plurality of lightning arrestors toestablish a potential gradient across the plurality of lightningarrestors.
 26. The method of claim 23, wherein biasing a first of thelightning arrestors to a different respective potential comprisesbiasing the first of the lightning arrestors to a potential that isbelow a corona discharge limit.
 27. The method of claim 23, whereinbiasing a first of the lightning arrestors to a different respectivepotential comprises connecting the first of the lightning arrestors toan EMF source.
 28. The method of claim 23, wherein biasing a first ofthe lightning arrestors to a different respective potential comprisesconnecting the first of the lightning arrestors to a capacitor and/or avoltage amplifier.
 29. The method of claim 23, wherein biasing a firstof the lightning arrestors to a different respective potential comprisesoperatively connecting the first of the lightning arrestors to aphotovoltaic array.
 30. The method of claim 23, wherein at least one ofthe plurality of lightning arrestors has a rod-, a rope-, a cable-, awire-, a netting-, a strip-, a plate-, a panel-, a wall-, and/or anextended surface-shape.
 31. The method of claim 23, wherein at least oneof the plurality of lightning arrestors is arranged to emit chargessubstantially non-directionally.
 32. The method of claim 23, wherein atleast one of the plurality of lightning arrestors is arranged to emitcharges substantially directionally.
 33. The method of claim 23, whereinthe first of the lightning arrestors and the second of the lightningarrestors are spaced less than a critical distance apart so that zonesof protection of the first and second lightning arrestors overlap. 34.The method of claim 23, wherein biasing a first of the lightningarrestors to a different respective potential comprises biasing thefirst of the lightning arrestors to a positive potential and biasing thesecond of the lightning arrestors to a negative potential.
 35. Themethod of claim 23, wherein biasing a first of the lightning arrestorsto a different respective potential comprises biasing the first of thelightning arrestors to a positive potential relative to a sitepotential, and biasing the second of the lightning arrestors to anegative potential relative to the site potential.
 36. The method ofclaim 23, wherein biasing a first of the lightning arrestors to adifferent respective potential comprises biasing a sequence of lightningarrestors positively and negatively.
 37. The method of claim 23, whereinbiasing a first of the lightning arrestors to a different respectivepotential comprises biasing a sequence of lightning arrestors positivelyand negatively with respect to a site potential.
 38. The method of claim23, wherein the plurality of lightning arrestors are deployed to protectan overhead AC transmission line from an atmospheric electricaldischarge.
 39. The method of claim 23, wherein biasing a first of thelightning arrestors to a different respective potential comprisesbiasing a sequence of lightning arrestors positively and negatively topotentials that have magnitudes greater than a peak line voltage in anoverhead AC transmission line.
 40. The method of claim 23, wherein theplurality of lightning arrestors are deployed to protect an overhead DCtransmission line from an atmospheric electrical discharge.
 41. Themethod of claim 23, further comprising, sensing a weather condition. 42.The method of claim 41, wherein biasing a first of the lightningarrestors to a different respective potential comprises biasing thefirst of the lightning arrestors in response to a sensed weathercondition and/or an anticipated weather condition.
 43. The method ofclaim 23, wherein biasing a first of the lightning arrestors to adifferent respective potential comprises biasing the first of thelightning arrestors in response to a local geopotential value.
 44. Themethod of claim 23, wherein biasing a first of the lightning arrestorsto a different respective potential comprises preparing a conductingpath from an overhead charge accumulation to ground.